Length adjustment mechanism



Nov. 2, 1965 G. 2. EDWARDS 3,214,809

LENGTH ADJUSTMENT MECHANISM Filed Dec. 20, 1963 ATTORNEYS United States Patent 3,214,809 LENGTH ADJUSTMENT MECHANlSM George Zahnor Edwards, Salt Lake City, Utah, assignor to Kedman Company, Salt Lake City, Utah, a corporation of Utah Filed Dec. 20, 1963, Ser. No. 332,136 8 (ll-aims. (Cl. 24-68) This invention relates to and constitutes an improvement on the length-adjustment mechanism which forms the subject of US. Patent No. 2,926,406 granted March 1, 1960 to me and George A. Langtord entitled Length Adjustment Mechanism.

The mechanism concerned is primarly intended to fit over and adjust the length of elongate overlapping parts that are formed as respective gear racks disposed in mutually spaced, confronting relationship, for example, the opposing ends of a normally closed loop headband for welders face-protective shields and helmets. It includes a spur gear and ring gear lock for positively holding any given size-adjustment made in the headband by means of a pinion in mesh with the gear racks. The pinion is rotated one way or another by an adjustment knob, which is turned manually after being pushed into unlocked position against the urge of a spring normally holding the aforesaid lock gears in adjustment-locking position.

Welders using face-protective devices equipped with headbands having the patented size-adjustment mechanism dislike having to push in the knob before turning it. As normally worn, the knob is located at the back of the head. Size adjustments are usually made with the headband in place on the head. It has been found that having to push in the knob against the opposing push of the spring, when the mechanism is so inconveniently located on the head, is annoying.

A principal object in the making of the present invention was to achieve the desired results of the patented invention, but in a manner which necessitates only turning the knob to achieve both unlocking of the mechanism and band-length adjustment.

A feature of the invention in achieving this object is the provision of carnming means between the knob and the locking spur gear, so that turning of the knob-anchored as it is against axial movementwill cause the locking spur gear to move axially away from the knob and out of mesh with the locking ring gear, against the urge of the spring which tends to hold it locked in mesh With such locking ring gear.

The camming means preferably takes the form of concentric, annular, mating sets of V-shaped teeth having sufiicient length to remain in mesh for pinion-turning purposes when the locking spur gear has been moved axially the maximum permissible distance to effect unlocking, whereby continued turning of the knob will rotate the size-adjusting pinion.

For smooth-working, positive operation, I have found that it is highly desirable that the mating teeth of the two annular sets of same be of radial formation with respect to the rotative axis of the adjustment knob, ascending in height progressively from the axial center and having, respectively, pairs of tooth-defining sides which meet at substantially ninety degree angles in forming the respective vertices of the teeth and the respective valleys lying between adjoining teeth.

Although the invention is especially useful in connection with length-adjusting mechanism as described, the concepts involved have broad application in the field of mechanical movements.

There is shown in the accompanying drawing a specific form of the invention as embodied in length or size adjustment mechanism for the headband of a face protector "ice or helmet for welders, which form represents what is presently regarded as the best mode of carrying out the generic concepts of the invention in actual practice. From the detailed description of this presently preferred form,

other more specific objects and features will become apparent.

In the drawing:

FIG. 1 represents a top plan view of a headband type of headgear for welding shields or helmets, the headband of same being adjustable in length by means of the mechanism of this invention;

FIG. 2, a fragmentary rear elevation of the headgear of FIG. 1;

FIG. 3, a fragmentary horizontal section taken on the line 3-3 of FIG. 2 and drawn to a considerably enlarged scale;

FIG. 4, a similar view showing the knob pushed out of locked position by the carnming teeth during headband adjustment;

FIG. 5, a perspective view of the several component parts of the mechanism in exploded relationship;

FIG. 6, a detail perspective view of the knob and locking gear assembly, looking toward the inside face thereof; and

FIGS. 7 and 8, elevations of the mating faces, respectively, of component molded plastic parts of the knob and locking gear assembly of FIG. 6.

Referring to the drawing:

As in the aforesaid Patent No. 2,926,406, the headgear shown in FIGS. 1 and 2 is adapted to fit on a welders head and mount a face-protective shield or helmet. It comprises a headband 10 formed from an elongate strip of suitable material, such as a tough and flexible plastic, and having its opposite ends 10a and 1%, FIGS. 3 and 4, configurated in well known manner as elongate gear racks. Such opposite ends are received and housed in mutually overlapping formation by an open-ended, flat, tubular casing 11 having a circular aperture 12 formed through its rear wall, preferably centrally thereof, and rimmed by a rearwardly extending annular wall 11a.

The gear racks, see 13, FIGS. 3 and 4, are disposed in mutually spaced, confronting relationship, being preferably formed along respectively opposite margins of elongate slots (not shown as such) provided similarly in the respective ends 10a and 10b of the headband strip. A pinion 14 of the length adjustment mechanism of this invention is disposed within such slots in mesh with the gear racks which are disposed above and below. Rotation of such pinion in one direction will increase the overlapping relationship of the ends 10a and Nb of the headband strip, while rotation of the pinion in the opposite direction will decrease such overlapping relationship.

In this way, headband strip 10 forms a closed loop, whose length is adjustable to accommodate a variety of different head sizes. A transverse strip 15 is provided in the usual manner to extend over the crown of the wearers head, and tubular projections 16 of cylindrical formation extend outwardly from the headband for pivotally receiving face-protective shield or helmet connecting means (not shown).

The length adjustment mechanism comprises a knob and spur gear assembly 17, see particularly FIG. 6, secured to but axially movable along a stub shaft 18, to which pinion 14 is rigidly secured (preferably by being molded integrally therewith, as shown) and which extends from such pinion toward aperture 12.

It is intended that turning of such knob and spur gear assembly 17 effect turning of the pinion 14 for headband length-adjustment purposes, and, to this end, the shaft 13 is splined or of polygonal formation, as shown, so as to snugly but slidably fit a similarly configurated receiving opening 19 formed centrally of the spur gear component 20 of such assembly 17.

Spur gear component 20 is a separate entity in the knob and spur gear assembly 17 of this improved mechanism, see FIG. 5, and is formed with a spur gear portion 20a and with a crown portion 20b composed of an annular set of cam teeth 21, the two portions being preferably integrally molded from plastic. The other component of the assembly, knob 22, is preferably also molded from plastic to provide an internal toothed portion 22a composed of an annular set of depending cam teeth 23 adapted to intermesh with the cam teeth 21 forming the crown of spur gear component 20. These intermeshing cam teeth constitute camming means arranged between and coupling together the knob and spur gear components, so that rotation of the knob will force spur gear portion 2% out of a normally assumed locking position relative to the locking gear means, which is provided by casing 11 in the form of a ring gear 24 internally of and integral with annular wall 11a.

Knob component 22 of the knob and spur gear assembly 17 is rotatable on shaft 25, which is of bolt formation and passes axially through pinion 14 and its poly onal stub shaft 18, as well as through both the knob and spur gear components of such assembly 17. Nut 25a secures the assembly in place.

A coil spring 26, compressed between spur gear component 20 and a washer 27, normally urges such spur gear component toward knob component 22 so that its toothed crown portion 20b is in close meshing engagement with the depending toothed portion 22a of such knob compo nent, as shown in FIG. 3. In order to adjust the length of headband 10, it is only necessary to turn knob 22 in one direction or the other. This is easily done while the headgear is in place on the head of a wearer.

During the first part of the turning or rotary motion imparted to the knob 22, the cam teeth 23 extending from its underside will bear against the contiguous cam teeth 21 extending from the spur gear component 20 and will tend to force such cam teeth 21 out of meshing engagement therewith. This will force spur gear component 20 away from knob component 22 along the rotative axis represented by the bolt of shaft 25 and will move locking spur gear portion 20a out of mesh with its interlocking ring gear 24, as shown in FIG. 4.

Spring 26 is such as to be fully compressed or to so resist further compression following disengagement of the interlocking gears that the series of cam teeth 21 and 23, respectively, do not entirely disengage as the turning of the knob continues, see the limited engagement 28, FIG. 4, remaining. Alternately, spur gear component 20 could be so dimensioned as to abut against washer 27 before cam teeth disengagement occurs. Thus, the continued turning of the knob will rotate the now unlocked spur gear component 2%) and, coincidentally, the pinion 14, which is coupled thereto by shaft 18. By reason of the intermeshing of pinion 14 with the mutually opposing gear racks a and 10b of headband 10, the length of such headband will be shortened or lengthened, depending upon which direction the knob is turned.

Upon release of the knob, it will be automatically forced back into the normal locked position of FIG. 3 by the force of spring 26.

As previously mentioned the meshing teeth camming arrangement, whereby both axial movement and rotary movement are achieved by turning a knob, is believed to be completely new in the combination here disclosed for accomplishing the advantageous results specified and also to be new in itself and useful in other combinations.

Whereas there is here illustrated and specifically described a certain preferred construction of apparatus which is presently regarded as the best mode of carrying out the invention, it should be understood that various changes may be made and other constructions adopted without departing from the inventive subject matter particularly pointed out and claimed herebelow.

I claim:

1. In length adjustment mechanism for a device having elongate overlapping parts formed as respective gear racks disposed in mutually spaced, confronting relationship, said mechanism comprising a casing for receiving and housing said overlapping parts, said casing being of open-ended tubular formation and having an aperture opening into its interior from the exterior thereof intermediate its length; a ring gear encircling the aperture and rigidly secured to the casing; a pinion within the casing in mesh with both said gear racks and having a shaft extending rigidly therefrom toward the aperture and concentric with the ring gear; a knob and spur gear assembly mounted concentrically on and engaging the shaft for rotating it and the pinion, the knob of said assembly being disposed externally of the casing at the aperture; resilient means normally urging said assembly so that the spur gear is brought into intermeshing engagement with the ring gear to lock said knob, spur gear, shaft, and pinion against rotation; and means retaining said assembly on the shaft, said assembly being slidable axially along the shaft against the urge of the resilient means for disengaging the spur gear from the ring gear and permitting rotation of said knob, spur gear, shaft, and pinion for length adjustment purposes, the improvement comprismg camming means arranged between and coupling said knob and said spur gear, so that rotation of the knob will cam the spur gear against the urge of said resilient means and slide it axially out of locking engagement with the ring gear.

2. The improvement of claim 1, wherein the camming means is in the form of concentric, annular, mating sets of V-shaped teeth having sufiicient length to remain in mesh for pinion-turning purposes after the spur gear has been cammed out of locking engagement with the ring gear.

3. The improvement of claim 2, wherein the mating teeth of each annular set of same are of radial formation, ascending in height progressively from the center of the set.

4. The improvement of claim 3, wherein the teeth are defined, respectively, by inclined sides which meet at substantially ninety degree angles in forming vertices for the teeth.

5. In combination, movable means mounted for rotation and for axial movement along the axis of rotation; means normally restraining said movable means against rotation; a rotatable element mounted for rotation about the same axis but anchored against movement along said axis and arranged to be rotated by an outside source; camming means between said rotatable element and said movable means, said camming means comprising sets of intermeshing teeth fixedly associated with said movable means and said element, respectively, for continuous interengagement, whereby the rotating of said element will serve, first, to move said movable means axially, away from said restraining means, and, then, to rotate said movable means; and means for limiting the extent of axial movement of said movable means to prevent separation of said sets of teeth beyond an efiective degree of intermesh.

6. The combination of claim 5, wherein the rotatable element is a knob adapted to be manually grasped and rotated, one of the sets of teeth being formed integrally with said knob.

7. The combination of claim 5, wherein each set of intermeshing teeth is circular and the individual. teeth are of radial formation, ascending in height progressively from the center of the set.

8. The combination of claim 7, wherein the teeth are defined, respectively, by inclined sides which meet at sub- 3,214,809 5 6 stantially ninety degree angles in forming vertices for 2,857,697 10/58 Schutt 7491 the teeth. 2,926,406 3/60 Edwards 24-68 FOREIGN PATENTS References Cited by the Examiner 5 228,689 6/60 Australla.

UNITED STATES PATENTS 2,205,742 6/40 Bowers 24-682 DONLEY I. STOCKING, Primary Examiner. 

1. IN LENGTH ADJUSTMENT MECHANISM FOR A DEVICE HAVING ELONGATE OVERLAPPING PARTS FORMED AS RESPECTIVE GEAR RACKS DISPOSED IN MUTUALLY SPACED, CONFRONTING RELATIONSHIP, SAID MECHANISM COMPRISING A CASING FOR RECEIVING AND HOUSING SAID OVERLAPPING PARTS, SAID CASING BEING OF OPEN-ENDED TUBULAR FORMATION AND HAVING AN APERTURE OPENING INTO ITS INTERIOR FROM THHE ETERIOR THEREOF INTERMEDIATE ITS LENGTH; A RING GEAR ENCIRCLING THE APERTURE AND RIGIDLY SECURED TO THE CASING; A PINION WITHIN THE CASING IN MESH WITH BOTH SAID GEAR RACKS AND HAVING A SHAFT EXTENDING RIGIDLY THEREFROM TOWARD THE APERTURE AND CONCENTRIC WITH THE RING GEAR; A KNOB AND SPUR GEAR ASSEMBLY MOUNTED CONCENTRICALLY ON AND ENGAGING THE SHAFT FOR ROTATING IT AND THE PINION, THE KNOB OF SAID ASSEMBLY BEING DISPOSED EXTERNALLY OF THE CASING AT THE APERTURE; RESILIENT MEANS NORMALLY URGING SAID ASSEMBLY SO THAT THE SPUR GEAR IS BROUGHT INTO INTERMESHING ENGAGEMENT WITH THE RING GEAR TO LOCK SAID KNOB, SPUR GEAR, SHAFT, AND PINION AGAINST ROTATION; AND MEANS RETAINING SAID ASSEMBLY ON THE SHAFT, SAID ASSEMBLY BEING SLIDABLE AXIALLY ALONG THE SHAFT AGAINST THE URGE OF THE RESILIENT MEANS FOR DISENGAGING THE SPUR GEAR FROM THE RING GEAR AND PERMITTING ROTATION OF SAID KNOB, SPUR GEAR, SHAFT, AND PINION FOR LENGTH ADJUSTMENT PURPOSES, THE IMPROVEMENT COMPRISING CAMMING MEANS ARRANGED BETWEEN AND COUPLING SAID KNOB AND SAID SPUR GEAR, SO THAT ROTATION OF THE KNOB WILL CAM THE SPUR GEAR AGAINST THE URGE OF SAID RESILIENT MEANS AND SLIDE IT AXIALLY OUT OF LOCKING ENGAGEMENT WITH THE RING GEAR. 